Center Fin Sliding in Fin Box

[808]

I tried to demo the Lopez thurster fins and when I tightened down the middle fin it still slides back and forth in the fin box. Anyone else ran into this before and know how to fix this. Thanks in Advance.

[dietlin]

Shim it.  Cut a piece of something (I've used a yoga mat) that you can line the bottom of the fin box with, then put the fin in and tighten it down.

[raf]

I've had to shim some JL fins as well.  I have access to a table saw also.  I cut a lexan strip the thickness of the fin base, 5-minute epoxied it to the base of the fin, then sanded it flush and until it fit the box just right.  The epoxy and lexan blend perfectly with the glass fin base. 

[EastFL]

My Lopez center did the same thing.  I just did a wrap of electric tape across the bottom and it fixed it.  Works fine. 

[jd]

Is it one of those fin boxes with the big square opening in the middle so the fin bolt drops straight in instead of the angle slot to slide the fin bolt in, which seems to be standard issue of any China import board?

Those fin boxes seem to be deeper than others.  Anyways, I've used a straw folded over, keeps the fin in nice and tight.

[808]

Thanks for all the help. It is a PSH board I believe you have to angle to square bolt to get it in. I come from short boarding so not allot of experience with these type of fin boxes.  Electric tape seams to be the ticket as I don't have access to a table saw that seams to be the best way. I have been running it as a quad but wanted to switch it up see how it rides. Hope you guys get some good surf over the holidays. Glad I am going to be able to make it work. My friend has the 9'2" and the fins fit perfect . I guess they put a bigger fin box on the 9'11" because it comes with a bigger fin.

[JohnnyMaya]

If it is not a huge gap, you can put some superglue on the surface of the fin base. Then wait until it dries and put some more. This will add a little volume and pattern to the fin base and it may be just enough to fill the gap.

CAUTION: THE SUPERGLUE HAS TO DRY BEFORE INSERTING FIN IN THE FIN BOX!!!

If it is to big of a gap go with the tape all along the fin base so that the stress from turning will be distributed all along the fin base. If you only put some tape in one end of the fin, it may lead to fin box failure. I've seen some finboxes starting to crack where the tape is. Or even worse, the glass around the fin box.

[PonoBill]

Take a careful look at the fin in the box before you do anything. If the fin slides it's because the tang with the screw hole is bottoming out on the crossbolt before the base of the fin is snug in the box. Sometimes this is because the tang is too thick. If you can push the fin down into the box  without the crossbolt in place and it gets snug when the base of the fin is even with the top of the fin box, then you might get a good fit by filing the tang a little thinner. You don't want to go too thin because it will break easily, but I've seen them be way too thick. If you just shim it you might have some of the base protruding out of the box, and that won't help performance.

[jd]

I have the PSH 9'11".  It has the crappy oversized china fin box I was referring to.  I also just received a Lopez tri set.  I think I know exactly what you are talking about.  The fin box is too deep for the fin.  Even if you tighten the fin bolt extremely tight the fin will still move.  I've lost a fin in this very type of box because of this. 

A McDonald's straw folded over and stuffed into the bottom of the box works like a charm.  It pushes the fin up high enough so you can get enough pressure on the fin to tighten it down without it moving.  No need to attempt to make some high tech shim. 

[808]

Thanks JD, how do you like it with the lopez tri fins compaired to the quad? When you say folded over did you take the straw and fold in half then put in the bottom of the fin box?

[mdsurf]

I've always liked the Quad setup and how it works.  I recently got a new board and set it up with the quad and then switched it out with the Trifin setup same day same waves ( no issue with the center fin in the box) and I really like the way the Thruster setup turns and cutsback and the way it paddles around to catch the wave.  I really love this setup.  I have another board I like the quads on it better.

I have a PSH and I like it equally as the quad and the tri.  I presently have it setup as a quad but with future controllers.

[jd]

808,

I just folded the straw in half or in thirds until it took up enough space in the bottom of the box to the point I felt the fin was tight enough.  I had the same problem with a similar sized fin on my other board with the same exact fin box.

I just got the Lopez tri set haven't had a chance to get them out in the water yet.  Rain here in Malibu and crappy conditions.  I will let you know as soon I get them in the water.  I've been using the Future quad Controllers and like them.  I rode the board with a 2+1 setup the first two times I rode it, but haven't gone back to the set up since getting the Controllers. 

[mdsurf]

I liked the difference the trifin made on my new sup... haven't even thought of changing them back and I love quads.